Having owned the Buck Strider tanto and Spyderco Military and also having had the chance to try the Benchmade 806, my personal choice would be the Military.
I found the Military to be the overall winner of these three when it came the utility. I liked the way it fit my hand best. It was also slim and discrete, unlike the Strider which I found to be overly think and heavy. Another couple of things I didn't like about the Strider were the coarseness of the G-10 handle (it actually wore out the edge of my pocket and waistband) and the fact that mine had some blade play that could not be eliminated. I really didn't like the tanto tip either, but you can get the spearpoint which in my opinion is the far better profile for utility purposes. The one I got had a BG-42 blade that was a bit of a bear to sharpen, but with enough persistence you could get it razor sharp. It also held an edge well.
The Military is light, strong and comfortable in the hand. The texture of the handle is great for grip, but not similar to course sandpaper like the Strider. I found the blade to be great for the type of use I put a knife to, which are general daily chores plus opening boxes and cutting plastic strapping. The Military really is a good knife. My first Military had an ATS-34 blade and my second one made from VG-10. Both are excellent steels that are fairly easy to sharpen and both held an edge really well, though I think the VG-10 held a slight edge in this department.
I also liked the AFCK very much, but do not like the coating Benchmade puts on the blade. I see no purpose for it as D2 is stain resistant enough not to have to worry about rust as long as even minimal care is used. I liked how this knife felt in my hand and really liked the profile of the blade. It was a great cutter. I didn't have it long enough to need to sharpen it, but I have had D2 blades in the past and they have presented no problem in this area. If you could get the blade with a satin finish this knife may well of ended up my favorite of the three.
Edited to add:
By the way, all of these knives had excellent locks. The Strider and Military use the liner lock and both were secure and easy to disengage. The Benchmade Axis lock was a pleasure to use.
Also, neither of the Militaries nor the AFCK had any blade play at all.